What to Pack:

Comfortable warm weather clothes! Bathing suits of course, maybe some flip flops, a speedo if you got one. It can chilly at night, but I don't think I have felt cold enough to wear pants. Sarah on the other hand gets cold easy, so plan accordingly.

As far as the wedding goes, wear something comfortable! No suits, no ties, nothing formal at all. If you don't want to tuck your shirt in, don't! I would suggest wearing sandles so you can take them off when walking on the beach.

If you forget something don't worry. Most things are easy to find and there is a Sam's Club, Walmart, and other stores with in walking distance.

A few things you might want to consider:
If you only remember two things...make those be your passport and ATM card!!
Dramamine: Even if you don't normally get sea sick, you might want to take some about an hour before the Catamaya. It's no fun to be sick on there!
iPod and portable speakers are nice to have for the hotel room
Bug spray
Sunscreen
Light jacket and a pair or two of capris (if you get cold easily!)
The Luna Blue has beach towels, so you don't need to take up space in your bag with these
Playa is very informal, you don't need dressy clothes
Imodium A-D or Pepto (just incase!)
Snorkel stuff if you have it/want it
Pair of tennis shoes or comfy walking shoes if you plan on going to the Tulum ruins or any excursions
Multiple bathing suits b/c that's what you'll wear the most
Room in your bag to buy stuff!
You're allowed to bring two bottles per person of alcohol back (Cuban rum is cool b/c it's illegal here!)
Sunglasses

That's all we can think of for now, but let us know if you have questions!